1. &lt;Background of the Invention&gt;
The present invention relates to an automatic focus control device for a camera, and particularly to an automatic focus control device which enables focus control while photographing a moving object.
2. &lt;Description of the Prior Art&gt;
A camera comprising an automatic focus (referred to as AF hereinafter) control device is so constructed that an integration of a light receiving element is executed for focus detection and the data generated from the receiving light element is converted from analogue to digital (referred to as A/D hereinafter) and inputted to a microcomputer in which the defocus amount of a photographic lens calculated. Then, the photographic lens is moved to the in-focus position on the basis of the calculation value for focus detection. Therefore, it takes a predetermined time for the photographic lens to reach the in-focus condition from the beginning of the calculation for focus detection, resulting in a time lag. If the defocus amount of the photographic lens of the camera for the object is changed due to the movement of the object during the time lag, the photographic lens which has finished the movement during the time lag tends to be out-of-focus for the object.
Therefore, it is necessary to enable the AF control to permit photographing a moving object. For example, according to the AF control shown in Japanese Patent Laid Opened No. 214325/1985, the position of the photographic lens is compensated in real time by repeating the calculation of the focus detection and by driving control of the photographic lens. In this case, however, the above mentioned control operation is only explained on the condition after the in-focus position for the object is once predetermined. In other words, the above mentioned operation is controlled on the premise condition that the photographic lens is set in the in-focus position for the object which is stopping or moving slowly first, subsequently the photographic lens is moved trackingly in order to obtain the in-focus condition for the moving object. However, there is no description of the way in the prior art how the in-focus condition can be obtained for the object moving in a high speed from the first.